Nutrients National Synthesis Project

Hydrogeologic Controls on the Transport and Fate of Nitrate
in Ground Water Beneath Riparian Buffer Zones: Results
From Thirteen Studies Across the United States

By Larry J. Puckett

[Water Science and Technology, vol. 49, no. 3]

Abstract
During the last two decades there has been growing interest in the
capacity of riparian buffer zones to remove nitrate from ground waters
moving through them. Riparian zone sediments often contain organic
carbon, which favors formation of reducing conditions that can lead to
removal of nitrate through denitrification. Over the past decade the
National Water Quality Assessment (NAWQA) Program has investigated the
transport and fate of nitrate in ground and surface waters in study
areas across the United States. In these studies riparian zone
efficiency in removing nitrate varied widely as a result of variations
in hydrogeologic factors. These factors include (1) denitrification in
the up-gradient aquifer due to the presence of organic carbon or other
electron donors, (2) long residence times (>50 years) along
ground-water flow paths allowing even slow reactions to completely
remove nitrate, (3) dilution of nitrate enriched waters with older
water having little nitrate, (4) bypassing of riparian zones due to
extensive use of drains and ditches, and (5) movement of ground water
along deep flow paths below reducing zones. By developing a better
understanding of the hydrogeologic settings in which riparian buffer
zones are likely to be inefficient we can develop improved nutrient
management plans.